[PappyCain]

Theoretically your boat would snag the chain on a mine and pull it down and contact would trigger the detonator. Today, the magnetic signature of the vessel would trigger the mine. Every part of the globe alters the signature of a boat's hull so a friendly today can pass a mine without detonation and un friendly' s signature would detonate the mine so we alter the signatures of the subs to operate in unfrendly waters. There were mines back then that were magnetic and any vessel in close proximity would detonate including friendlies. Mine sweepers had wood hulls as did many escorts who help pilot ships in mined areas. So you may have been the approripriate distance away from detonation for a era magnetic or contact mine.